The studies involving mutagenesis by chemical carcinogens and the role of altered microsomal biotransformation in the liver will continue. The effort will be directed toward an attempt to establish the critical parameters indicating mutagenicity so that in further studies involving altered endoplasmic reticulum all parameters do not have to be measured. The parameters to be tested will include the content of cytochrome P-450, aryl hydroxylase activity, aminopyrine demethylase activity, and aniline hydroxylase activity. In addition microsomal protein, microsomal phospholipids, the electron microscopic appearance of hepatocytes, as well as the mutagenic ability of the carcinogen or its metabolite will be tested to see which parameter relates best under the various circumstances to mutagenesis. Furthermore, the question will attempt to be answered whether a carcinogen induces its own metabolism more than nonspecific induction with phenobarbital or polychlorinated biphenyls, and hence alters its mutagenicity more specifically than does nonspecific induction. The potential of environmental pollutants by pesticides to become mutagens and therefore carcinogens will also be tested using the system involving hepatic microsomes and bacteria.